Naples has a Mediterranean climate, with hot, dry summers in the mid-90s. This coincides with peak travel season, from May to September. Naples is already the most densely populated city in Europe, so its version of crowded trumps even the most visited continental cities. August is a particularly rough time to visit; pretty much the entire country is on holiday, so many restaurants and hotels are either closed or filled with Italian tourists, who flock to the coasts. The tourist season also brings higher hotel and restaurant prices—both of which fill a lot further in advance.
You can also expect to see high costs around Easter, when Naples hosts a huge parade, and Christmas, when hundreds of nativity scenes are on display. During New Year’s, tourists arrive to enjoy one of Italy’s grandest fireworks displays.
You’ll find better deals and fewer crowds during the shoulder seasons, specifically from September through November and in the early spring. Naples has a rainy stretch from December to March, but for the rest of the year, the weather is pretty ideal. Other than during the summer, temperatures average in the 50s, and breezes off of the Bay of Naples keep the air fresh—even in southern Italy’s biggest city.